This invention relates to scroll-type fluid apparatus such as scroll-type vacuum pumps, scroll-type compressors and the like. More particularly, it relates to a scroll-type fluid apparatus which has an inlet chamber accommodating therein first and second scroll members which cooperate to define a variable volume chamber in the inlet chamber. More specifically, the invention is concerned with such an apparatus capable of effectively preventing lubricant, which lubricates and seals the first and second scroll members, from leaking from the inlet chamber to a drive chamber accommodating a drive means for driving the scroll members.
FIG. 11 shows a typical example of a conventional scroll-type fluid apparatus in the form of a scroll-type vacuum pump. Referring to the Figure, the illustrated scroll-type vacuum pump has a cylindrical housing 101, in which a pair of, i.e., upper and lower, disk-like partitioning walls 102 are disposed one above another. Between the partitioning walls 102 and 103 is defined an inlet chamber 105 in the form of a pump chamber communicating with an intake port 104. A drive chamber 106 is defined by the lower partitioning wall 103 and the cylindrical peripheral surface and bottom surface of the housing 101. An annular spacer 107 is interposed between the upper and lower partitioning walls 102 and 103. The spacer 107 is secured to the annular peripheral wall of the housing 101, and the upper and lower partitioning walls 102 and 103 are secured by bolts or the like to the respective upper and lower end surfaces of the spacer 107.
In the pump chamber 105 there is disposed a pair of, i.e., first and second scroll members 110 and 111 one above another. The first scroll member 111 in the form of a drive scroll member has a lower end disk 111a and a spiral drive scroll vane 111b integral with and projecting from the center of the top of the lower end disk 111a. The lower surface 111a of the lower end disk 111a is rotatably supported on the upper surface of the lower partitioning member 103 via a thrust bearing 112. The lower end disk 111a has a shaft 111c extending downward from its center and penetrating the lower partitioning member 103. The shaft 111c is rotatably supported in a central part of the lower partitioning wall 103 via a pair of, i.e., upper and lower, bearings 113. The second scroll member 110 in the form of a driven scroll member has an upper end disk 110a facing in parallel to the top of the lower end disk 111a of the drive scroll member 111 and a spiral driven scroll vane 110b which is integral with and projects from the neighborhood of the center of the lower surface of the upper end disk 110a. A shaft 110c extending upwardly from the center of the upper surface of the upper end disk 110a is rotatably supported substantially in a central part of the upper partitioning wall 102 via a pair of, i.e., upper and lower, bearings 114. The axis 01 of the shaft 110c is eccentric by a fixed distance L with respect to the axis 02 of the shaft 111c of the lower end disk 111b. The distance L is given as EQU L=P/2-t
where P represents the pitch of the scroll vanes 110b and 111b (i.e., the distance between adjacent vanes) and t represents the width (i.e., thickness) of the scroll vanes 110b and 111b.
The scroll vanes 110b and 111b of the driven and drive scroll members 110 and 111 are disposed such that they are in mesh with each other with their respective upper and lower end surfaces in contact with the inner surfaces of the upper and lower end disks 110a and 111a. Between these scroll vanes are defined several crescent variable-volume chambers 115 with their volumes being varied with the rotation of the driven and drive scroll members 110 and 111. The driven and drive scroll vanes 110b and 111b have their respective upper and lower end surfaces formed with spiral seal grooves, in which seal members 116 and 117 are accommodated to effect hermetical seals between the upper and lower end surfaces of the scroll vanes 110b and 111b on one hand, and the corresponding inner surfaces of the upper and lower end disks 110a and 111b on the other hand. A thrust bearing 118 is disposed between the upper surface of the upper end disk 110a and lower end surface of the upper partitioning wall 102. The upper end disk 110a and the shaft 111c are each formed at their central part with an exhaust duct 119 axially penetrating them. The upper end of the exhaust duct 119 is connected to one end of an exhaust tube 120, the other end portion of which extends to the outside of the housing 101.
The top of the upper partitioning wall 102 has an integral central annular projection 121 defining an annular oil reservoir 121a open at the top. The oil reservoir 121a is sealed by removably mounting a cover 122 by means of bolts 128 on the top surface of the projection 121. It is connected via an oil supply duct 124 to an oil pump 123 disposed in the drive chamber 106, and it can supply oil, i.e., lubricant, 125 through the oil supply duct 124 with the operation of the oil pump 123. The oil 125 in the oil reservoir 121a is supplied via radial and axial oil ducts 126 and 127 formed in the shaft 110c of the drive scroll member 110 to the variable-volume chambers 115 formed between the driven and drive scroll vanes 110b and 111b. Thus, it lubricates the contact parts of the driven and drive scroll vanes 110b and 111b and upper and lower end disks 110b and 111a during rotation of the driven and drive scroll members 110 and 111, and it also effects a hermetical seal between contact parts S of the inner and outer peripheral surfaces of the scroll vanes 110b and 111b (see (a) in FIG. 12). The oil 125 having lubricated the rotational contact parts of the drive and driven scroll vanes 110b and 111b is discharged along with compressed gas through the exhaust duct 119 to the outside, while it is partly collected in a lower portion of the pump chamber 105 to leak around the outer periphery of the shaft 111c into the drive chamber 106 so as to be collected in a lower portion thereof.
The inner surface of the cover 122, which is fitted on the projection 121 of the upper partitioning wall 102, is provided with a stationary mechanical seal 130 surrounding the duct 120 penetrating the cover 122. The upper end of the shaft 110c extending from the upper end disk 110b into the oil reservoir 121a is provided with a rotational mechanical seal 131 surrounding the exhaust duct 120. The lower end of the fixed mechanical seal is urged by the upper surface of the rotational mechanical seal 131, so that a hermetical seal is provided between the contact parts of the exhaust duct 119 and the exhaust tube 120.
Disposed in the drive chamber 106 is a rotary drive means 133 in the form of a motor having an output or rotary shaft 133a thereof made integral at the upper end thereof with the shaft 111c of the lower end disk 111a. The motor 133 has a stator 135 secured by a support 134 to the peripheral wall of the housing 101 and a rotor 136 secured to the shaft 133a. The shaft 133a has its lower end portion coupled to the oil pump 123. Thus, with the rotation of the motor 133, the oil pump 123 is driven, whereby the oil 125 collected in a lower portion of the drive chamber 106 is supplied through the oil supply duct 124 to the oil reservoir 121a.
The above-described scroll-type vacuum pump operates as follows. When the motor 133 is energized, the drive scroll member 111 is thereby caused to rotate through the motor shaft 113a about an axis 0.sub.2 thereof. In this state, as shown at (b) in FIG. 12, in left-side contacting portions or lines A which are formed by contacting between the driven and drive scroll vanes 110b and 111b of the driven and drive scroll members 110 and 111 and which are located on the left side of the central axis 0.sub.2 of the motor shaft 113a, the outer peripheral surface of the driven scroll vane 110b of the driven scroll member 110 is in contact with the inner peripheral surface of the drive scroll vane 111b of the drive scroll member 111. At the left-side contacting portions A, the inner periphery of the driven scroll vane 120b undergoes motion at this time such that its radius is decreasing. Therefore, the rotation of the drive scroll vane 111b causes synchronous rotation of the driven scroll vane 110b while being in contact with the outer periphery of driven scroll vane 110b. Since the center of rotation O.sub.2 of the drive scroll vane 111b is eccentric with respect to the center of rotation O.sub.1 of the driven scroll vane 110b, the volumes of the variable-volume chambers 115 defined between the drive and driven scroll vanes 111b and 110b are progressively decreasing with the synchronous rotation of the scroll vanes, thus gradually compressing the gas in the variable-volume chambers 115. While the drive and driven scroll vanes 111b and 110b are synchronously rotated for gas compression, the reaction torque accompanying the gas compression in the variable-volume chambers 115 defined between the scroll vanes is applied evenly to both of the drive and driven scroll vanes 111b and 110b. The reaction torque applied to the drive scroll vane 111b is partially canceled by the output torque of the motor 133. On the other hand, the driven scroll vane 110b tends to be rotated by the applied reaction torque about the axis O.sub.1 of the shaft 110 in the direction opposite to the direction of rotation of the drive scroll vane 111b. This reverse rotation, however, is prevented by the contact between the outer periphery of the driven scroll vane 110b and the inner periphery of the drive scroll vane 111b in the contacting portions A, as shown at (b) in FIG. 12. Therefore, with the rotation of the drive scroll vane 111b, the volumes of the variable-volume chambers 115 are gradually decreasing to compress the gas therein. When the gas is compressed to a minimum volume, the variable-volume chambers 115 are placed into fluid communication with the exhaust duct 119, whereupon the compressed gas under a high pressure is discharged or exhausted through the exhaust duct 119 and the exhaust tube 120 to the outside. In this way, the gas in the pump chamber 105 is exhausted to the outside, thus generally reducing the inner pressure therein.
As described above, the driven scroll member 110 is driven to rotate with the rotation of the drive scroll member 111. If, however, the driven scroll member 110 tends to be rotated faster than the drive scroll member 111 , the driven scroll vane 110b is gradually separated from the drive scroll vane 111b in the portions A as shown at (b) in FIG. 12, thus producing gaps between these scroll vanes. For this reason, no drive force is transmitted from the driven scroll vane 110b to the drive scroll vane 111b. In the above state, however, in contacting portions or lines B which are formed by contacting between the drive and driven scroll vanes 11b, and which are located on the right side of the central axis O.sub.1 of the shaft 110c as illustrated at (b) in FIG. 12, the radius of the inner periphery of the driven scroll vane 110b is decreasing, while the radius of the outer periphery of the drive scroll vane 111b is increasing. As a result, the contact between the inner periphery of the driven scroll vane 110b and the outer periphery of the drive scroll vane 111b is rapidly increased or strengthened to provide for braking. Thus, faster rotation of the driven scroll vane 110b than that of the drive scroll vane 111b is automatically restricted.
When the motor 133 is stopped, the drive scroll member 111 begins to decelerate. At this time, the driven scroll member 110 tends to be rotated at a speed higher than that of the drive scroll member 111 due to its inertia. In this state, in the portions B at (b) in FIG. 12, the contact between the inner periphery of the driven scroll vane 110b and outer periphery of the drive scroll vane 111b is increased, and the driven scroll vane 110b is decelerated by the drive scroll vane 111b so that both the scroll vanes 110b, 111b are rotated synchronously.
With the known scroll vacuum pump having the above construction, however, if water vapor or corrosive gas is contained in the gas drawn into the pump, it is very likely that water or corrosive matter is introduced into the oil 125 in the pump chamber 105. In a such case, the oil 125 is liable to cause corrosion, reduction in electrical insulation and the like of the motor 133 which is accommodated in the drive chamber 106. Therefore, the scroll-type vacuum pump can find only specific and limited applications where there arises no problem even if water or corrosive matter is introduced into the lubricant oil.